CN105548770A - Pulse laser equivalent LET value calculating method for SOI device - Google Patents

Abstract

The invention relates to a pulse laser equivalent LET value detection method, comprising the following steps: after the silicon substrate of the SOI device is removed, the SOI device is irradiated and scanned to obtain the incident laser energy at which the single event effect of the SOI device occurs; according to air, Refractive index of buried oxide layer and silicon, reflection and transmission coefficient of laser from air to buried oxide layer, reflection and transmission coefficient from buried oxide layer to air, reflection and transmission coefficient from buried oxide layer to silicon, and from silicon to buried oxygen layer The reflection and transmission coefficients of the layer are used to calculate the energy transmittance of the laser passing through the buried oxide layer of the SOI device; the spot influence parameters are calculated according to the laser spot radius when reaching the sensitive area and the lateral size of the sensitive area; according to the incident laser energy, energy The transmittance and spot influence parameters determine the equivalent LET value of the pulsed laser. The method can obtain the key index LET value of the device single event effect sensitivity rapidly, at low cost and more accurately.

Description

A Calculation Method of Pulse Laser Equivalent LET Value of SOI Device

technical field

The invention relates to the technical field of space radiation, in particular to a pulse laser equivalent LET value detection method of an SOI device.

Background technique

The single event effect is one of the most important ionizing radiation effects that affect the space reliability of devices, and it seriously threatens the safe and reliable operation of spacecraft in orbit. The evaluation of device resistance to single event effects is generally carried out using high-energy heavy ion accelerators and proton accelerators. However, due to practical problems in the operation and operation of large-scale test devices such as heavy ions and proton accelerators, the cycle and cost of single-event effect evaluation tests will often be greatly increased, and even seriously hinder the normal development of devices and the smooth completion of space missions. Compared with the large-scale accelerator test device, the single event effect test method of pulsed laser simulation device has precise single event effect space and time resolution characteristics, continuously adjustable energy, no radioactivity, no need for vacuuming, convenient operation, high test efficiency, and low cost. low-level features. Therefore, as an effective single event effect evaluation method, pulsed laser has been widely used at home and abroad, and has become an effective means for single event effect evaluation and protection design verification. In recent years, pulsed laser simulation single event effect test devices have been established at home and abroad, forming a fast and low-cost device single event effect sensitivity evaluation capability.

LET (LinearEnergyTransfer, linear energy transfer) value is one of the key engineering technical indicators to evaluate the sensitivity of aerospace electronic devices to single event effects. Because the physical mechanism of the single event effect of the pulsed laser and the heavy ion induced device is not completely the same, and in the actual experiment, the laser spot size after focusing is limited by the laser wavelength, focusing device, optical diffraction, etc., the ionization track width of the laser is larger than that of the heavy ion The ionization track width of is much larger. In addition, with the improvement of device integration, the metal layer on the front side of the device is becoming more and more dense, the test technology of pulsed laser front incident irradiation device is greatly limited, and the test technology of pulsed laser back irradiation device is widely used, but for In the case of laser back-irradiated devices, the multilayer structure of the device can significantly affect the delivery of laser energy. These make the accurate calculation of the corresponding equivalent LET value of the single event effect induced by the pulsed laser energy become the main technical problem restricting the application of the pulsed laser simulation single event effect test method in engineering practice.

Compared with traditional bulk silicon devices, SOI (Silicon on Insulator, silicon on insulator substrate) is separated by a buried oxide layer between the device and the substrate, and the device is only manufactured in a very thin silicon film on the surface, as shown in the figure 1. In FIG. 1 , 101 is a source region, 102 is a gate, 103 is a drain region, 104 is a buried oxide layer, and 105 is a substrate. STI (ShallowTrenchIsolation) is a shallow trench isolation region in the SOI structure process. n refers to an n-type doped region in the SOI structure. This unique structure makes SOI devices have no latch-up effect of traditional bulk silicon MOS (Metal-Oxide-Semiconductor, Metal-Oxide-Semiconductor) devices, and has better radiation resistance. However, because the structure of SOI devices is different from that of traditional bulk silicon process devices, the existing calculation methods for equivalent LET values of pulsed lasers are based on typical bulk silicon process device structures. When applied to SOI devices, the accuracy is low .

Contents of the invention

Based on this, it is necessary to provide a pulsed laser equivalent LET value detection method for SOI devices to solve the problem of low accuracy in the prior art.

A pulse laser equivalent LET value detection method of an SOI device, comprising the following steps:

After removing the silicon substrate of the SOI device, the SOI device is irradiated and scanned to obtain the incident laser energy for the single event effect of the SOI device;

According to the refractive index of air, buried oxide layer and silicon, the reflection and transmission coefficient of laser from air to buried oxide layer, the reflection and transmission coefficient from buried oxide layer to air, the reflection and transmission coefficient from buried oxide layer to silicon, and the reflection and transmission coefficient from silicon Reflection and transmission coefficients to the buried oxide layer, calculate the energy transmittance of the laser passing through the buried oxide layer of the SOI device;

According to the laser spot radius when reaching the sensitive area and the lateral size of the sensitive area, the spot influence parameter is calculated;

The equivalent LET value of the pulsed laser is determined according to the incident laser energy, energy transmittance and spot influence parameters.

The pulse laser equivalent LET value detection method of the above-mentioned SOI device is to calculate the incident laser energy of the SOI device, the energy transmittance of the laser passing through the buried oxide layer of the SOI device, and the light spot by performing irradiation scanning on the SOI device from which the silicon substrate has been removed. Influence parameters, and determine the pulse laser equivalent LET value according to the incident laser energy, energy transmittance and spot influence parameters, this method can be used for pulse laser simulation single event effect test evaluation of SOI devices in aerospace, aviation and ground electronic systems Among them, the LET value, a key indicator of device single event effect sensitivity, can be obtained quickly, at low cost and more accurately.

Description of drawings

Figure 1 is a SOI structure diagram;

Fig. 2 is the method schematic diagram of prior art;

Fig. 3 is the flow chart of calculation method of pulsed laser equivalent LET value of SOI device of the present invention;

Fig. 4 is a schematic diagram of an SOI device in which the laser back incident removes the substrate;

Fig. 5 is a schematic diagram of multi-beam interference of laser light passing through the buried oxide layer;

Figure 6 is a schematic diagram of the modulation variation of the transmittance of the 800nm laser with the thickness of the buried oxide layer;

Fig. 7 is a one-dimensional schematic diagram of a laser spot with energy Gaussian distribution covering a single event effect sensitive area.

detailed description

An embodiment of the method for calculating the pulsed laser equivalent LET value of the SOI device of the present invention will be described below with reference to the accompanying drawings.

As shown in Figure 2, the existing pulsed laser equivalent LET calculation method is aimed at typical bulk silicon process devices, in the test mode of laser backside irradiation devices, considering the energy attenuation and accumulation of the pulsed laser during the transmission process in the chip substrate material , analyze the impact of the metal wiring on the front of the device and the inner surface of the substrate on the reflection of multiple laser oscillations, and calculate the energy values of all pulsed lasers that contribute to the single event effect in the sensitive area. Then the equivalent LET is calculated according to the equivalent principle of laser energy and heavy ion LET value. In Fig. 2, 201 is the back of the device, 202 is the laser beam, 203 is the silicon substrate, 204 is the active area, 205 is the laser focal plane, 206 is the front of the device, 207 is the passivation layer, 208 is the metal layer.

The technical solution in the prior art is established based on the structure of a typical bulk silicon process device, and the structure of an SOI device is different from that of a typical bulk silicon process device, so this technology is not applicable to an SOI device. A major feature of the existing technology is the consideration of multiple oscillations and reflections of the laser in the device substrate, but its calculation is based on the ideal conditions of laser transmission and devices, and the parameters involved in the calculation process are difficult to measure in practical applications. With the reduction of the device process size, the size of the laser spot is much larger than the size of the single event effect sensitive area. Therefore, the influence of the laser spot size needs to be considered in the calculation of the equivalent LET of pulsed laser energy, but the existing technology does not consider it.

In order to solve the above problems, the present invention provides a method for calculating the equivalent LET value of a pulsed laser. As shown in Figure 3, the pulsed laser equivalent LET value calculation method may include the following steps:

S1, after removing the silicon substrate of the SOI device, the SOI device is irradiated and scanned to obtain the incident laser energy for the single event effect of the SOI device;

Similar to the laser delivery process shown in Figure 2, the SOI device is irradiated by pulsed laser backside incidence. Because SOI has interfaces of different media such as air/Si (silicon) substrate, Si substrate/SiO ₂ (silicon dioxide), etc., the laser will reflect at the interface, and then multiple oscillation reflections will occur in the Si substrate. The thickness of the Si substrate of the device is generally several hundred micrometers. When the laser passes through such a thick Si, serious absorption and attenuation will occur, which will seriously affect the laser energy incident on the active region of the device. Assuming that the incident energy of the laser is E0, the number of reflections is n, the total energy loss after passing through the Si layer for the i-th time is ΔEi, i=1, 2,...,n, then the final outgoing laser energy is E0-ΔE2n. These complicate the calculation and testing process of laser energy transmission, making it difficult to obtain accurate results. For the influence of Si substrate on the incident laser energy, the existing calculation methods are based on the ideal conditions of laser energy transmission and devices, and the parameters involved in the calculation process are difficult to measure in practical applications, which is equivalent to the pulsed laser LET The calculation caused a large error. Therefore, before performing irradiation scanning on the SOI device, the silicon substrate of the SOI device can be removed, thereby improving calculation accuracy. The SOI device silicon substrate can be removed by etching.

XeF ₂ (xenon difluoride) is a commonly used working gas in plasma etching and reactive etching of Si. During etching, XeF ₂ gas will be adsorbed on the silicon surface, and even in the absence of external energy, XeF ₂ will spontaneously decompose to produce xenon and fluorine, and fluorine can etch silicon wafers at a relatively high rate at room temperature . The main advantages of XeF ₂ etching are: firstly, it is a dry etching, and its etching reaction products can be pumped out by a vacuum system, and there is basically no etching pollution; secondly, this etching has a high selectivity for many materials. Ratio, such as silicon dioxide, silicon nitride, aluminum and photoresist, etc., among which the etching selectivity ratio of XeF ₂ to silicon dioxide can be as high as 1000:1. The buried oxide layer of SOI devices is generally SiO ₂ material. Therefore, XeF ₂ has a high etching selectivity to Si/SiO ₂ and is very suitable for etching and removing Si substrates of SOI devices.

The basic process of removing the Si substrate of SOI devices by _XeF2 reactive etching may include the following steps:

First, the back of the SOI device can be desealed by an acid etch deseal method. For common plastic-encapsulated and metal-encapsulated devices, the method of acid corrosion and unsealing is generally used.

Then, the front side of the unsealed SOI device can be filled with potting compound. In this way, it can ensure that the device is not damaged during the XeF ₂ reactive etching process.

Finally, the filled SOI device can be etched in a XeF ₂ reactive etching device until all the silicon material on the substrate of the SOI device is etched away, exposing the surface of the buried oxide silicon dioxide layer.

As shown in Figure 4, the SOI device after removing the Si substrate by laser back incident irradiation completely avoids the reflection, refraction, absorption attenuation and other effects of the substrate on the laser incident. In FIG. 4 , 401 denotes a laser, 402 denotes a Si substrate, 403 denotes a buried oxide layer, 404 denotes an active region, and 405 denotes an epoxy resin.

For the single event effect test of the pulsed laser simulation device, the whole test device is generally irradiated and scanned by the step-scan test method, and finally the incident laser energy E ₀ for the single event effect of the device is obtained. Laser power is measured with a laser power meter adapted to the respective laser wavelength.

S2, according to the refractive index of air, buried oxide layer and silicon, the reflection and transmission coefficient of laser from air to buried oxide layer, the reflection and transmission coefficient from buried oxide layer to air, the reflection and transmission coefficient from buried oxide layer to silicon, and From the reflection and transmission coefficients of silicon to the buried oxide layer, calculate the energy transmittance of the laser through the buried oxide layer of the SOI device;

Specifically, the step of calculating the energy transmittance of the laser passing through the buried oxide layer of the SOI device may include:

Calculate the phase difference of two adjacent transmitted beams;

calculating the complex amplitude of the total transmitted beam from said phase difference;

Calculate the transmission coefficient of the laser according to the complex amplitude of the transmitted beam and the amplitude of the incident beam;

The energy transmittance is calculated according to the transmittance coefficient.

As shown in FIG. 4 , for the SOI device after the Si substrate is removed, the laser is incident on the surface of the buried oxide layer (for example, SiO ₂ ) from the back, and then enters the active region of the device after passing through the buried oxide layer. According to the principle of laser transmission, due to the existence of two interfaces: air/buried oxide layer and buried oxide layer/Si, the laser will experience multiple reflections and refractions on its transmission path. Since the thickness of the buried oxide layer is generally several hundred nanometers, which is generally smaller than the laser wavelength used in the laser test, the laser beam passing through the buried oxide layer will produce multi-beam interference, and the buried oxide layer has a modulating effect on the transmittance of laser energy. . For the equivalent LET calculation of pulsed laser, the influence of the buried oxide layer on the laser energy should be determined first, that is, the energy transmittance T of the laser passing through the buried oxide layer should be calculated.

Since the irradiation method of the laser simulation single event effect test is that the laser is vertically incident on the back of the device, only the normal incident situation is considered when calculating the transmittance of the laser through the buried oxide layer. As shown in Fig. 5, set the refractive index of air 501, buried oxide layer 502 and Si503 as n ₀ , n, n _S respectively, set the reflection and transmission coefficients of the laser from air to buried oxide layer as r ₁ and t ₁ , and reflect The reflection and transmission coefficients from buried oxide layer to air are r′ ₁ and t′ ₁ , r ₁ =-r′ ₁ ; the reflection and transmission coefficients from buried oxide layer to Si are r ₂ and t ₂ , and from Si to buried The reflection and transmission coefficients of the oxygen layer are r' ₂ and t' ₂ , r ₂ =-r' ₂ , and the thickness of the buried oxide layer is d. The amplitude of the incident beam is E _0i , omitting the common initial phase, the phase difference of two adjacent transmitted beams is:

$\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, k is the wave vector of the laser light wave transmission, the value is equal to 2πn/λ, and λ is the wavelength of the laser in vacuum. The total complex amplitude of the transmitted beam is the sum of the amplitudes of the individual transmitted beams:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 02</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 03</span>}\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; ...</span>}\\ <span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Then the transmission coefficient of the laser is:

$\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; t</span>}}}{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

According to the Fresnel formula:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; t</span>}{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

The transmittance T is:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

And substituting the respective reflection coefficients r ₁ , r ₂ and transmission coefficients t ₁ , t ₂ into formula (5), the final result can be obtained:

$\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; t</span>}{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; sin</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Taking the 800nm laser, which is a common wavelength for laser simulation of single event effects, as an example, the refractive index of air is 1, the refractive index of the buried oxide layer is 1.5, and the refractive index of Si is 3.65. The calculated transmittance of the laser through the buried oxide layer The modulation changes with the thickness of the buried oxide layer are shown in Figure 6.

S3, calculating the spot influence parameter according to the laser spot radius when reaching the sensitive area and the lateral size of the sensitive area;

With the shrinking of the device process size, for devices with sub-micron or even smaller process sizes, the size of the laser spot is much larger than the size of the single event effect sensitive area. For example, in a typical 90nm process SOISRAM (Static Random Access Memory), the size of the single event flipping sensitive area is 0.2 microns, and the size of the laser focus spot is limited by factors such as the laser wavelength and the diffraction effect during laser transmission. For example, for a commonly used laser with a wavelength of 590nm, the diameter of the focused spot should be greater than 1 micron. Therefore, the influence of laser spot size on laser energy deposition must be considered in the calculation of pulsed laser energy equivalent LET, which is represented by the spot influence parameter F.

Fig. 7 is a one-dimensional schematic diagram of the laser spot covering the single event effect sensitive area, and the energy distribution of the laser spot is a Gaussian distribution in the lateral direction. In Fig. 7, 701 indicates the single event effect sensitive area, 702 indicates the area covered by the laser spot, 703 indicates the Si active area, and 704 indicates the SiO ₂ buried oxide layer. Assuming that the center of the laser spot is consistent with the center of the single event effect sensitive area, the two-dimensional laser energy distribution function in the single event effect sensitive area is:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; E.</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

In the formula, E is the energy of the laser pulse incident into the sensitive area, x and y are the coordinates of the laser spot in the sensitive area, ω is the radius of the laser spot when it reaches the sensitive area, because the thickness of the sensitive area is very small, such as a typical The thickness of the sensitive area of the 90nm SOI device is about 70nm, and the change of the spot size in the longitudinal direction can be ignored, so ω is a constant. The effective laser energy in the sensitive area is the integral of the laser energy distribution in the sensitive area:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; E.</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

In the formula, a and b are the lateral dimensions of the sensitive area, which are generally determined according to the process of the device. For example, the size of the sensitive area of CMOS (Complementary Metal Oxide Semiconductor, Complementary Metal Oxide Semiconductor) SRAM single event flipping is up to NMOS (N-Metal-Oxide-Semiconductor , N-type metal-oxide-semiconductor) and PMOS (P-Metal-Oxide-Semiconductor, P-type metal-oxide-semiconductor) drain region size. The above formula can be written as:

E _sv =E·F(9)

Then the parameter F of the effect of the spot size on the laser energy deposition is:

$\begin{array}{c}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}\mathrm{<span\; class="notranslate">\; v</span>}}}{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}^{\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}\\ <span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Taking the above-mentioned laser with a wavelength of 590nm as an example, the laser spot radius is 0.83 microns, and the lateral size of the single particle inversion sensitive area is 0.2 microns. Considering the influence of the spot size on the laser energy deposition, the calculation result of the parameter F is about 0.034. It can be seen that after considering the spot size, the effective laser deposition energy is 3.4% of the original. On the contrary, if the influence of the laser spot size is not considered, a huge error will be generated in the calculation of the equivalent LET of the pulsed laser energy.

S4. Determine the equivalent LET value of the pulsed laser according to the incident laser energy, energy transmittance, and spot influence parameters.

According to the definition of LET value:

$\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

ρ is the density of the incident semiconductor material. The pulsed laser passes through the buried oxide layer and enters the Si active region. Under the laser energy linear absorption mechanism, one photon is absorbed to generate an electron-hole pair. The attenuation law of the laser energy with the incident depth x obeys Beer's law, and the equivalent weight of the pulsed laser is The ion let values are:

$\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;E</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; \&alpha;E</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Therefore, in the sensitive area of the device, the equivalent LET value of the pulsed laser is:

$\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;E</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

In the formula, ELET is the equivalent LET value of the pulsed laser, λ is the wavelength of the pulsed laser, E _ion is the energy required for heavy ions to excite a pair of electron-hole pairs, ρ is the density of the incident semiconductor material, and h is the Planck constant, c is the speed of light, l is the thickness of the sensitive area of the single event effect, E ₀ is the laser energy incident on the surface of the buried oxide layer, T is the transmittance of the buried oxide layer, F is the influence parameter of the light spot, and α is the active area of the laser on the silicon The absorption coefficient in the region.

It should be noted that the pulse width of the pulsed laser, the nonlinear optical absorption effect and other influencing factors need to be controlled in the experiment to be insufficient to affect the above calculation method. The wavelength λ of the pulsed laser ranges from 250nm to 1130nm, and the buried oxide layer material includes but not limited to SiO ₂ material.

Compared with the existing technical solutions, the present invention establishes a pulsed laser equivalent LET calculation method suitable for SOI device structures by using _XeF2 to etch silicon in reaction:

(1) The Si substrate of the SOI device is removed by XeF ₂ reactive etching, so that the pulsed laser is directly incident on the surface of the buried oxide layer when the back is irradiated, avoiding the multiple oscillation and reflection process of the laser in the device substrate, and making the pulse The laser equivalent LET calculation is greatly simplified, increasing the accuracy of the final calculation results. At the same time, due to the elimination of the absorption and attenuation effect of the substrate on laser energy, the laser wavelength range that can be used for pulsed laser simulation single event effect experiments is greatly increased.

(2) The influence of the buried oxygen layer on the transmitted laser energy was analyzed, the calculation method of the transmittance was determined, and the result that the energy transmittance was modulated by the thickness of the buried oxide layer after the laser passed through the buried oxide layer was obtained.

(3) The influence of the laser spot size on the laser energy inducing the single event effect was analyzed, the calculation method of the spot influence parameter F was determined, and the influence result of the spot size parameter on the effective laser energy was obtained.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the patent scope of the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (9)

1. a pulse laser equivalent LET value detection method of SOI device, is characterized in that, comprises the following steps: After removing the silicon substrate of the SOI device, the SOI device is irradiated and scanned to obtain the incident laser energy for the single event effect of the SOI device; According to the refractive index of air, buried oxide layer and silicon, the reflection and transmission coefficient of laser from air to buried oxide layer, the reflection and transmission coefficient from buried oxide layer to air, the reflection and transmission coefficient from buried oxide layer to silicon, and the reflection and transmission coefficient from silicon Reflection and transmission coefficients to the buried oxide layer, calculate the energy transmittance of the laser passing through the buried oxide layer of the SOI device; According to the laser spot radius when reaching the sensitive area and the lateral size of the sensitive area, the spot influence parameter is calculated; The equivalent LET value of the pulsed laser is determined according to the incident laser energy, energy transmittance and spot influence parameters. 2. The method for calculating the pulsed laser equivalent LET value of an SOI device according to claim 1, wherein the buried oxide layer includes but not limited to _SiO2 material. 3. the pulsed laser equivalent LET value calculation method of SOI device according to claim 1, is characterized in that, before carrying out radiation scanning to SOI device, also comprises the following steps: Etching and removing the silicon substrate of the SOI device. 4. the pulsed laser equivalent LET value calculation method of SOI device according to claim ₃ is characterized in that, utilizes XeF Reactive etching removes SOI device silicon substrate. 5. the pulsed laser equivalent LET value calculation method of SOI device according to claim ₄ , is characterized in that, utilizes XeF Reactive etching removes the step of SOI device silicon substrate to comprise: Unseal the back of the SOI device by acid etching unsealing method; Fill the front side of the unsealed SOI device with potting compound; Put the filled SOI device into a XeF ₂ reactive etching device for etching until all the silicon material on the substrate of the SOI device is etched away, exposing the surface of the buried oxide silicon dioxide layer. 6. the pulsed laser equivalent LET value calculation method of SOI device according to claim 1, is characterized in that, the step of calculating the energy transmittance of laser light through the buried oxide layer of SOI device comprises: Calculate the phase difference of two adjacent transmitted beams; calculating the complex amplitude of the total transmitted beam from said phase difference; Calculate the transmission coefficient of the laser according to the complex amplitude of the transmitted beam and the amplitude of the incident beam; The energy transmittance is calculated according to the transmittance coefficient. 7. the pulsed laser equivalent LET value calculation method of SOI device according to claim 6, is characterized in that, the step of calculating described transmittance according to described transmittance coefficient comprises: Calculate the energy transmittance according to the following formula: $\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>$ In the formula, T is the energy transmittance, n _S and n ₀ are the refractive indices of silicon and air respectively, t ₁ is the transmission coefficient of the laser from the air to the buried oxide layer, and t ₂ is the transmission coefficient of the laser from the buried oxide layer to the silicon Transmission coefficient, δ is the phase difference, i is the number of adjacent projected beams, r ₁ is the reflection coefficient of the laser from air to the buried oxide layer, and r ₂ is the reflection coefficient of the laser from the buried oxide layer to silicon. 8. the pulsed laser equivalent LET value calculation method of SOI device according to claim 1, it is characterized in that, according to the laser spot radius when reaching sensitive zone and the lateral dimension of sensitive zone calculates the step of spot influence parameter comprising: The speckle influence parameter is calculated according to the following formula: $\begin{array}{c}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; V</span>}}}{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\underset{<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\overset{\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}}\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; x</span>}\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}\\ <span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; \&pi;\&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; a</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; b</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>\end{array}<span\; class="notranslate">\; ,</span>$ In the formula, F is the influence parameter of the light spot, E is the energy of the laser pulse incident into the sensitive area, E _SV is the effective laser energy in the sensitive area, which is the integral of the laser energy distribution in the sensitive area, and a and b are the sensitive The lateral size of the area, ω is the radius of the laser spot when it reaches the sensitive area. 9. The method for calculating the pulsed laser equivalent LET value of the SOI device according to claim 1, wherein the step of calculating the pulsed laser equivalent LET value according to the energy transmittance and light spot influence parameters comprises: Calculate the equivalent LET value of the pulsed laser according to the following formula $\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; E.</span>}\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&lambda;E</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; no</span>}}}{\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$ In the formula, ELET is the equivalent LET value of the pulsed laser, λ is the wavelength of the pulsed laser, E _ion is the energy required for heavy ions to excite a pair of electron-hole pairs, ρ is the density of the incident semiconductor material, and h is the Planck constant, c is the speed of light, l is the thickness of the sensitive area of the single event effect, E ₀ is the laser energy incident on the surface of the buried oxide layer, T is the transmittance of the buried oxide layer, F is the influence parameter of the light spot, and α is the active area of the laser on the silicon The absorption coefficient in the region.